﻿588 
  ANNUAL 
  REPORT 
  SMITHSONIAN" 
  INSTITUTION, 
  192 
  9 
  

  

  produced 
  an 
  intellectual 
  chill, 
  but 
  Chamberlin 
  's 
  logical 
  insight 
  

   penetrated 
  the 
  superficial 
  appearances 
  and 
  discovered 
  the 
  deeper 
  

   question. 
  Back 
  of 
  the 
  drift 
  phenomena 
  was 
  a 
  mysterious 
  cause 
  of 
  

   climatic 
  change. 
  To 
  discover 
  it 
  became 
  his 
  main 
  purpose, 
  and 
  the 
  

   search 
  conducted 
  him 
  through 
  an 
  investigation 
  of 
  the 
  origin 
  of 
  the 
  

   atmosphere 
  to 
  a 
  theory 
  of 
  the 
  evolution 
  of 
  the 
  solar 
  system. 
  

  

  Led 
  by 
  him 
  with 
  an 
  intellectual 
  leadership 
  that 
  has 
  never 
  been 
  

   questioned, 
  a 
  group 
  of 
  able 
  geologists 
  has 
  analyzed 
  the 
  drift 
  sheets 
  of 
  

   North 
  America, 
  mapped 
  their 
  extent 
  and 
  detailed 
  structure, 
  and 
  

   contributed 
  a 
  thorough 
  understanding 
  of 
  the 
  Pleistocene 
  record. 
  It 
  is 
  

   a 
  great 
  contribution. 
  It 
  demanded 
  capacity 
  for 
  intimate 
  and 
  dis- 
  

   criminating 
  observation 
  of 
  differences 
  where 
  others 
  saw 
  sameness 
  — 
  for 
  

   careful 
  and 
  alternative 
  interpretation 
  on 
  the 
  basis 
  of 
  process, 
  stage, 
  

   and 
  environment, 
  for 
  balanced 
  judgment 
  and 
  impartial 
  testing 
  of 
  

   probabilities. 
  It 
  called 
  for 
  those 
  qualities 
  which 
  Chamberlin 
  already 
  

   possessed 
  to 
  a 
  high 
  degree 
  but 
  which 
  he 
  was 
  to 
  train 
  to 
  even 
  more 
  

   difficult 
  tasks. 
  

  

  As 
  the 
  complexity 
  of 
  the 
  glacial 
  periods 
  became 
  more 
  evident, 
  the 
  

   enigma 
  of 
  the 
  cause 
  grew 
  more 
  impressive. 
  No 
  satisfactory 
  solution 
  

   had 
  been 
  proposed, 
  as 
  appeared 
  on 
  testing 
  the 
  current 
  theories 
  by 
  

   the 
  accumulating 
  facts. 
  None 
  was 
  possible 
  under 
  the 
  accepted 
  

   doctrine 
  of 
  atmospheric 
  evolution 
  from 
  the 
  steaming 
  envelope 
  of 
  a 
  

   molten 
  globe 
  to 
  the 
  present 
  life-giving 
  air. 
  The 
  enigma 
  deepened 
  

   and 
  broadened 
  as 
  the 
  eager 
  but 
  patient 
  student 
  searched 
  not 
  only 
  

   geology 
  but 
  aU 
  allied 
  sciences 
  for 
  clues. 
  

  

  He 
  gives 
  Tyndall 
  credit 
  for 
  the 
  suggestion 
  that 
  led 
  him 
  to 
  consider 
  

   the 
  relation 
  between 
  climatic 
  conditions 
  and 
  the 
  constitution 
  of 
  the 
  

   atmosphere. 
  The 
  proportion 
  of 
  carbonic 
  acid 
  appeared 
  to 
  be 
  a 
  

   critical 
  factor. 
  The 
  variables 
  involved 
  in 
  its 
  variation 
  were 
  found 
  by 
  

   Chamberlin 
  to 
  link 
  geological, 
  chemical, 
  and 
  biological 
  processes 
  in 
  

   cycles 
  of 
  mutual 
  reactions. 
  The 
  antiquity 
  of 
  recurrent 
  climatic 
  

   changes 
  turned 
  the 
  investigation 
  back 
  from 
  the 
  Pleistocene 
  to 
  the 
  

   pre-Cambrian 
  glaciations, 
  and 
  thus 
  to 
  the 
  origin 
  of 
  the 
  atmosphere. 
  

  

  The 
  inquirer 
  could 
  not 
  pause 
  there. 
  The 
  atmosphere 
  of 
  a 
  molten 
  

   earth 
  indeed 
  suggested 
  tremendous 
  possibilities, 
  but 
  they 
  were 
  not 
  com- 
  

   patible 
  with 
  the 
  facts 
  of 
  terrestrial 
  history, 
  so 
  far 
  as 
  we 
  can 
  read 
  it. 
  

   The 
  progress 
  of 
  knowledge 
  had 
  pushed 
  a 
  possible 
  molten 
  state 
  of 
  the 
  

   earth 
  even 
  further 
  back 
  into 
  vague 
  traditional 
  stages 
  of 
  creation. 
  

  

  Contrary 
  to 
  all 
  that 
  he 
  had 
  been 
  taught, 
  Chamberlin 
  found 
  himself 
  

   obliged 
  to 
  consider 
  alternative 
  hypotheses 
  that 
  might 
  be 
  consistent 
  

   with 
  a 
  less 
  spectacular 
  evolution, 
  and 
  he 
  was 
  forced 
  to 
  examine 
  

   critically 
  the 
  very 
  foundations 
  of 
  the 
  geologic 
  faith 
  of 
  that 
  day. 
  

  

  He 
  described 
  his 
  early 
  work 
  on 
  theories 
  of 
  the 
  genesis 
  of 
  the 
  earth 
  as 
  

   resembling 
  the 
  exploration 
  of 
  an 
  old 
  mine 
  to 
  find 
  what 
  of 
  value 
  was 
  

   left 
  in 
  the 
  outworked 
  leads 
  and 
  to 
  discover 
  what 
  promising 
  veins 
  

  

  